When I wrote "air into space", I didn't mean it reached escape velocity. Rather, it no longer acted as a pressure cover to the blast. The air have gone up a few

When I wrote "air into space", I didn't mean it reached escape velocity. Rather, it no longer acted as a pressure cover to the blast. The air have gone up a few hundred km and returned to earth. FWIW, there was a pressure wave world-wide. The Wikipedia page says a fluctuation of 0.6 mbar was measured in New Zealand. (Krakatoa's pressure wave was recorded going around the Earth three times!) That said, let's consider the number of Tsar Bomba's needed to lower the pressure by 0.01mBar, permanently, assuming all of the energy from the bomb was used to get air to exactly escape velocity. (In reality, energy also went into space, or melted snow, or was turned into seismic energy, or ... And there will be a distribution of velocities.) Mass of the atmosphere is about 5.15E18 kg. 0.01mBar is 1/100,000 reduction in atmosphere gives 5.15E13 kg. Escape velocity about 11 km/sec. Energy = 1/2 m v * v = 3E21 J. Tsar Bomba = 210–240 PJ = 2E17 J. So, assuming the impossibly perfect transfer of all energy into moving air at escape velocity, 10,000 Tsar Bombas. I don't know how many orders of magnitude more are needed before the spherical cap of atmosphere would be blasted to escape velocity, but clearly even a tera-ton bomb isn't enough.